Updates in QA task IO and checker

In this merge request, the subdirectory model of the QA-task output was changed from TFolder to TDirectoryFile. There are two reasons of the modification. Firstly, the TFolder class is a legacy code and is not recommended to be used. Secondly, the reading many objects from a TFolder rapidly causes memory usage increase (even if one simply calls gFile->FindObjectAny("a_folder")).